HEMODYNAMIC MONITORING
Joshua Goldberg, MD
Assistant Professor of Surgery
Associate Medical Director, Burn Unit
UCHSC
Definitions and Principles
The measurement and interpretation of
biological systems that describe
performance of the cardiovascular
system
Monitoring is NOT therapy
Clinicians must know how to interpret
the data
Very few randomized controlled trials
Oxygen Delivery is the Goal
Oxygen Delivery
DO2 (mL O2/min) = CO (L/min) x CaO2 (mL O2/dL) x 10
CO (L/min) = HR (beats/min) x SV (L/beat)
CaO2 (mL O2/dL) = [1.34 x (Hb)(g/dL) x SaO2] + [.003 x PaO2 mm Hg]
Oxygen Consumption
CVO2 (mL O2/dL) = [1.34 x (Hb)(g/dL) x SVO2] + [.003 x PVO2 mm Hg]
VO2 (mL O2/min) = CO x 3(CaO2 CVO2) x 10
Determinants of Cardiac
Performance
Preload
Afterload
Estimated by end-diastolic volume
(pressure)
CVP for RVEDV, PAOP (wedge) for LVEDV
SVR = [MAP-CVP]/CO x 80
Contractility
Methods of Hemodynamic
Monitoring
Arterial Blood Pressure
Non-invasive
Direct arterial pressure measurement
Central Venous Pressure
The Pulmonary Artery Catheter
Cardiac Output Measurement
Tissue Oxygenation
Non-invasive Blood Pressure
Monitoring
Non-invasive Blood Pressure
Measurement
Manual or automated devices
Method of measurement
Oscillometric (most common)
Auscultatory (Korotkoff sounds)
MAP most accurate, DP least accurate
MAP is calculated
Combination
Limitations of Non-invasive
Blood Pressure Monitoring
Cuff must be placed correctly and must be
appropriately sized
Auscultatory method is very inaccurate
Korotkoff sounds difficult to hear
Significant underestimation in low-flow (i.e. shock)
states
Oscillometric measurements also commonly
inaccurate (> 5 mm Hg off directly recorded
pressures)
Direct Arterial Blood Pressure
Measurement
Indications for Arterial
Catheterization
Need for continuous blood pressure
measurement
Respiratory failure
Hemodynamic instability
Vasopressor requirement
Frequent arterial blood gas assessments
Most common locations: radial, femoral,
axillary, and dorsalis pedis
Complications of Arterial
Catheterization
Hemorrhage
Hematoma
Thrombosis
Proximal or distal embolization
Pseudoaneurysm
Infection
Pseudoaneurysm
Limitations of Arterial
Catheterization
Pressure does not accurately reflect
flow when vascular impedance is
abnormal
Systolic pressure amplification
Mean pressure is more accurate
Recording artifacts
Underdamping
Overdamping
Waveform Distortion
Central Venous Catheterization
Central venous pressure
Right atrial (superior vena cava) pressure
Limited by respiratory variation and PEEP
Central venous oxygen saturation
SCVO2
Correlates with SMVO2 assuming stable cardiac
function
Goal-directed resuscitation in severe sepsis and
septic shock (Rivers, et al)
Central Venous Pressure
Waveform
The Pulmonary Artery
Catheter
HJC Swan and sailboats
Widespread use in critically ill patients
Remains controversial
Lack of prospective, randomized trials
PAC data are only as good as the clinicians
interpretation and application
Measures CVP, PAP, PAOP, Cardiac
Index and SVO2
Pulmonary Artery Catheter
Indications for Pulmonary
Artery Catheterization
Identification of the type of shock
Cardiogenic (acute MI)
Hypovolemic (hemorrhagic)
Obstructive (PE, cardiac tamponade)
Distributive (septic)
Many critically ill patients exhibit elements
of more than 1 shock classification
Monitoring the effectiveness of therapy
Normal Hemodynamic Values
SVO2
60-75%
Stroke volume
50-100 mL
Stroke index
25-45 mL/M2
Cardiac output
4-8 L/min
Cardiac index
2.5-4.0 L/min/M2
MAP
60-100 mm Hg
CVP
2-6 mm Hg
PAP systolic
20-30 mm Hg
PAP diastolic
5-15 mm Hg
PAOP (wedge)
8-12 mm Hg
SVR
900-1300 dynes.sec.cm-5
Hemodynamic Profiles in
Shock
Class of
Shock
Cardiogenic
Hypovolemic
Hyperdynamic
septic
Hypodynamic
septic
CVP
PAOP
CO/CI
SVR
Pulmonary Artery Catheter
Placement
Complications of Pulmonary
Artery Catheterization
General central line complications
Pneumothorax
Arterial injury
Infection
Embolization
Inability to place PAC into PA
Arrhythmias (heart block)
Pulmonary artery rupture
The Pulmonary Artery
Catheter Controversy
Accuracy of data affected by many
conditions common in critically ill
patients
Lack of prospective randomized data
supporting better outcomes with PAC
Limited by the ability of the clinician to
accurately interpret PAC data
Cardiac Output Measurement
Multiple techniques
Thermodilution most common
Transpulmonary
Pulse contour analysis
Esophageal Doppler
Newer pulmonary artery catheters offer
continuous cardiac output measurement
Thermodilution Method of
Cardiac Output Measurement
Tissue Oxygenation
Despite advances, our ability to monitor
the microcirculation and tissue
perfusion is limited
Laboratory tests for metabolic acidosis
are global and insensitive
Newer technology on the horizon
Gastric tonometry
Sublingual capnometry
Conclusions
Multiple different methods of
hemodynamic monitoring
Keys to success
1)
2)
3)
Know when to use which method
Technical skills for device placement
Know how to interpret the data
Remember the limitations of the
technology
